GB2038903A - Advancing Apparatus for a Winning Machine - Google Patents

Abstract

An advancing apparatus for a winning machine 5 positively guided along a conveyor 1 has two clamp feet 15, 17 arranged offset relative to one another in direction of movement of the winning machine. The clamp feet are connected by longitudinally directed, hydraulically pressurizable thrust-piston-like advancing units 17, 18, 19, 20 to the winning machine, alternatingly arrestable at a guide rail 2 provided at conveyor and provided with hydraulically pressurizable thrust- piston-like releasing units 29. The advancing apparatus furthermore possesses a hydraulic control automatically alternatingly pressurizing with work fluid or relieving from the work pressure the thrust-piston units 17-20. Each clamp foot 15, 16 is connected via two oppositely directed advancing units 17, 18 or 19, 20 shiftable simultaneously in counterdirection to the winning machine and is arrestable by mechanical clamp elements forming a component of the clamp feet 15, 16 at the guide rail 2. The clamping of the clamping elements is releasable by pressurizing a releasing unit, the releasing units of the clamp feet being hydraulically interlocked mutually. <IMAGE>

Description

SPECIFICATION Advancing Apparatus for a Winning Machine This invention relates to an advancing apparatus for a winning machine positively guided along a cross cut conveyor, in particular a machine of a cutting type, preferably for the side area of the cross cut having two clamp feet arranged offset relative to one another in direction of movement of the winning machine, said clamp feet being connected by longitudinally directed, hydraulically pressurizable thrust-piston-like advancing units to the winning machine, alternatingly arrestable at a guide rail provided at the cross cut conveyor and provided with hydraulically pressurizable thrust-piston-like releasing units, and furthermore possessing a hydraulic control automatically alternatingly pressurizing with work fluid or relieving from the work pressure the thrust-piston units.

A cutting machine including these features belongs to prior art as a result of its publication in the magazine "Industrie Min6rale-Mine", June 1975, pages 1 to 12. Each clamp foot of this known cutting machine is connected to the machine body only by a single hydraulically pressurizable thrust-piston unit. Both advancing units extend from the clamp feet in the same direction. Their piston rods are connected to the clamp feet, and their cylinders are connected to the machine body. While the piston spaces of the advancing units are directly connected to a control pump, lines lead from the piston rod spaces of the advancing units to an auxiliary cylinder in which a floating piston is axially shiftable. The piston is located on a rod passing through the cylinder in longitudinal direction and is also freely shiftable relative to said rod.On the rod, abutments are secured endwise of the piston stroke. The rod is in communication with a reversing valve.

When for instance the piston space of an advancing unit is pressurized, the work fluid contained in the piston rod space of this advancing unit shifts the floating piston in the auxiliary cylinder. Thereby, the work fluid contained on the other side of the floating piston is transferred to the piston rod space of the other advancing unit so that the piston of this advancing unit is shifted opposite to the shifting direction of the pressurized piston, but with the same velocity. The countermovement occurs when the other advancing unit in turn is pressurized. Valves in the interior of the pistons of both advancing units are respectively opened at the stroke end by abutments and thereby permit initiation of movement, venting of the auxiliary cylinder and a synchronized motion of the advancing units.

In the clamp shoes, there are arranged a plurality of hydraulically pressurizable thrustpiston units which are pressurizable on both sides and which upon a suitable pressurization arrest the respective clamp foot at the guide rail of the cross cut conveyor. These thrust-piston units thus attend both to the function of the clamping and releasing units.

A disadvantage of the conventional advancing apparatus is considered to be that the clamp feet are exclusively arrested at the guide rail be means of the hydraulic work fluid and also released therefrom again. Upon a breaking of a fluid line or in the event of some other damage in the hydraulic control system, it is not possible to instantaneously locally arrest the winning machine. Another disadvantage by virtue of the single advancing unit associated with each clamp foot resides in the fact that the advancement in the two directions of movement cannot be effected with the same force. Also, there are no provisions of correlating the advancing force to the engagement momentum existing at the tools of the winning machine.Finally, it cannot be precluded with the conventional advancing apparatus that in case of trouble in the hydraulic control system a clamping force already builds up in one clamp foot when the other clamp foot is still clamped to the guide rail or when the releasing units concurrently defining the clamping units are already pressurized when the releasing units of the other clamp foot are likewise still pressurized. Damages at the mechanical and hydraulic elements of the winning machine, in particular of the advancing apparatus, however, are the inevitable result.

Regarding the conventional advancing apparatus it is to thus be ascertained that the safety precuations, in particular when operating the winning machine in down-inclined cross cuts, are insufficient. Also, the different advance thrust in both directions of movement is a disadvantage.

It is, therefore, the object of the present invention in setting out from the conventional advancing apparatus to improve same in such a manner that the associated winning machine is able to be moved in both directions of movement always with the same advance force and that trouble in the hydraulic control system brings about no danger for the miners and the winning operation.

To attain this object the present invention provides an advancing apparatus for a winning machine positively guided along a cross cut conveyor, in particular of a cutting type, preferably for the side area of a cross cut, having two clamp feet arranged offset relative to one another in direction of movement of the winning machine, said clamp feet being connected by longitudinally directed, hydraulically pressurizable thrust-pistonlike advancing units to the winning machine, alternatingly arrestable at a guide rail provided at the cross cut conveyor and provided with hydraulically pressurizable thrust-pston-like releasing units, and futhermore possessing a hydraulic control automatically alternatingly pressurizing with work fluid or relieving from the work pressure the thrust-piston units, wherein each clamp foot is connected via two oppositely directed advancing units shiftable simultaneously in counterdirection to the winning machine and is arrestable by mechanical clamp elements forming a component of the clamp feet at the guide rail, the clamping of the clamping elements being releasable by pressurizing a releasing unit, the releasing units of the clamp feet being hydraulicaily interlocked mutually.

Such an advancing apparatus, which is in particular used for a winning machine only operated in the cross cut edge area, accordingly possesses a total of four hydraulically pressurizable thrust-piston-like advancing units of which respectively two are associated with one clamp foot. By the fact that the advancing units, starting from the clamp feet, on the one hand are directed in the one and on the other hand in the other direction of movement, they are able to be pressurized such that always one advancing unit acts pulling and the other pushing. The advancing units preferably connected with their piston rods to the clamp feet are therefore on the one hand regarding the piston space and on the other hand regarding the piston rod space pressurized simultaneously.By virtue of this arrangement, now in contradistinction to the conventional advancing apparatus an advancement is possible in both directions of movement always with the same force.

A further advantage of the advancing apparatus proposed by the present invention resides in the fact that the clamping of the clamp feet to the guide rail is exclusively effected by mechanical clamp elements while the releasing of the clamping of the clamp feet is effected by means of the hydraulic work fluid via the thrustpiston-like releasing units. This measure ensures that in case of trouble in the hydraulic control system by virtue of line fracturing or other damages, in conjunction with a pressure drop, the mechanical clamp elements in all cases arrest the winning machine locally.By the mutual hydraulic interlocking action of the releasing units of the clamp feet, it is ensured that a releasing pressure in the releasing units is able to build up only in the event there is a pressureless condition at the other clamp foot and thereby this clamp foot is automatically arrested at the guide rail.

In the further developement of the thought which underlies the invention the advancing units may be pressurizable by a twin-control pump adjustable in correlationship to the engagement momentum existing at the tools of the winning machine via two separate supply lines. The twincontrol pump permits a proper synchronous movement of the advancing units in both directions of movement. Also, the twin-control pump permits the introduction of independent advancing forces and advancing rates. In addition thereto, it is of an advantage that the advancing rate or the advancing force is able to be correlated to the engagement momentum respectively existing at the tools of the cross cut machine, for instance at a cutting roll. Thereby, an optimum coaction is achievable between advancing force, advancing rate and engagement momentum.

Basically, it suffices when the adjustment elements of the twin-control pump are connected to a thrust-piston unit capable of being influenced at one side by a control signal of the cutting roll, said thrust-piston unit on the other side being spring-biased. The pressure space of the thrustpiston unit also is in communication with the supply container via a controllable restriction.

When the momentum at the cutting roll increases, also the control pressure rises, and the piston of the thrust-piston unit is shifted against the action of the spring force. Thereby, the adjustment of the pump is altered proportionally in the sense of a reduced advancing rate, but an increased advancing force.

An advantageous feature of the invention is that in the supply lines between the twin-control pump and the advancing units there are incorporated reversing valves which are hydraulically controllable depending on the position of limit switches associated with the winning machine and coacting with the clamp feet. The limit switches formed as hydraulic valves are conveniently secured to the machine body and are contacted at the stroke end of the advancing units by the clamping feet. In the inoperative condition, the limit switches block the supply of control fluid to the control connections of the reversing valves. Merely at the stroke end of the advancing units, the limit switches are shortly shifted in counteraction to the resetting force of springs and thereby the pressurization of the advancing units is reversed in the sense of a work or neutral stroke.

In this context, it is then considred to be of sense that both the limit switches and thecontrol connections of the reversing valves are located in an auxiliary control circuit which is pressurizable by an auxiliary circuit pump which is connected to a motor possibly also driving the twin-control pump.

For structural reasons, the motor, for instance an electric motor, the auxiliary circuit pump and the twin-control pump may beerranged on one and the same shaft. Thus, there are provided two hydraulic circuits separated from one another which are also able to be pressure-controlled independent of one another. This on the one hand involves the work circuit between the twincontrol pump and the advancing units and on the other hand the auxiliary control circuit between the auxiliary circuit pump and the releasing units and the control connections of the reversing valves, respectively. Upon an advancing operation of the winning machine accordingly either by the advancing units both clamp feet are moved to the centre of the machine, one clamp foot being released and the other being arrested at the guide rail so that the machine is advanced, or both clamp feet are moved toward the ends of the winning machine. This operation is always effected alternatingly consecutively. When one clamp foot has reached an end position, it moves into the area of the associated limit switch, and the movement operation is reversed. The directional reversion of the advancing units thus is effected by the hydraulically controlled reversing valves, which in turn are controlled by the auxiliary control circuit.This auxiliary control circuit furthermore provides for a releasing of the clamp feet, the releasing units associated with the clamp feet bringing about the releasing operation in counteraction to the effect of the mechanical clamping elements.

So that a correct controlling of the reversing valves is able to be ensured, the invention furthermore contemplates that in the auxiliary control circuit between the auxiliary circuit pump and the control connections of the reversing valves there is incorporated a precontrol valve hydraulically reversible depending on the position of the limit switches. This precontrol valve thus ensures that either the one or the other control connection of the reversing valves receives control fluid and thus the reversing valves are concurrently shifted.

In order to store the respective control condition which occurs only for a short period of time up to the next control operation, a further advantageous feature of the invention is that in the control lines between the limit switches and the control connections of the precontrol valve there may be incorporated an automatically unlockable dual check valve.

So that trouble in the hydraulic control has no negative effect in safety aspects, a further advantageous feature of the invention is considered to be that the releasing units only pressurizable unilaterally may be connected via hydraulically unlockable check valves to the auxiliary control circuit. In this context it is then of a further advantage that the check valves locking to the releasing units are connected respectively via an opening control line to the auxiliary control circuit between the precontrol valve and the control connections of the reversing valves, further check valves blocking to the supply container being connected to the supply lines between the check valves and the releasing units, said further check valves respectively being connected via an opening control line to the control line which leads to the check valve connected to the other supply line.Such an arrangement thus ensures that a releasing pressure at the releasing units is able to build up only in the event the respectively other control fluid line is pressureless. This occurs by a connection of this line to one of the unlockable check valves to the supply container, the opening being caused by applying counter-pressure.

A reversion of the advancing movement of the winning machine principly can be effected in that either the releasing operation of the clamp feet or the controlling of the advancing units is reversed.

According to another feature of the invention it is preferred that in the auxiliary control circuit between the precontrol valve and the control connections of the reversing valves there is incorporated a control valve preferably reversibly manually. In this case consequently the controlling of the advancing units is exchanged.

The configuration of the mechanical clamping elements in the clamp feet may be solved in various ways. It must merely be ensured that for failing control fluid the clamping elements automatically ensure in a mechanical fashion that the clamp feet are arrested at the guide rail.

An advantageous embodiment of the invention, however, is one in which the clamping elements have a guided clamping wedge which is pressurizable in direction of a clamping jaw encompassing the guide rail by means of a spring and in counterdirection by means of a releasing unit. The clamping jaw is formed in two parts, orie of said parts being fixedly connected to the housing accommodating the clamping elements.

The other part of the clamping jaw is movable about an axis extending in longitudinal direction of the guide rail and influenceable by the wedging action of the clamping wedge. The clamping wedge is guided between the clamping jaw and an interior wall of the housing. It is preferably formed L-shaped, between the top side of the horizontal limb of the clamping wedge and the cover of the housing a helical compression spring being able to be arranged. This helical compression spring accordingly shifts the clamping wedge at all times in direction of the clamping jaw. The bottom side of the horizontal limb of the clamping wedge is in communication with a thrust-piston-like releasing unit which on the other hand is likewise supported on the housing.If this releasing unit is pressurized, the clamping wedge is shifted against the resetting force of the spring, and the clamping jaw then loosely engages the guide rail. In the event of failing control fluid, the spring again takes over the task of urging the clamping wedge against the clamping jaw and thus of arresting the clamp foot at the guide rail.

The invention furthermore finally provides for that the clamping elements are respectively arranged in housings which are inserted in the clamp feet likewise formed housing-like without any substantial clearance in longitudinal direction thereof, but with clearance in transverse and vertical direction. This embodiment permit to arrange in an array a plurality of clamping elements in each clamp foot. The clearance in transverse and vertical direction permits a conforming of the individual clamp feet to the course of the guide rail even in the event same is provided with alignment errors or damaged portions. In longitudinal direction, however, there is only a shifting clearance between the individual clamping element housings or between the clamping element housings and the clamp foot housing, since there a force effect prevails.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 is a diagrammatical perspective illustration of a cross cut side winning machine in the form of a cutting machine positively guided along a cross cut conveyor; Fig. 2 is a vertical cross section, on an enlarged scale, of a clamping element housing, and Fig. 3 is a circuit diagram of the hydraulic control defining a component of the advancing apparatus of the cross cut side winning machine.

Fig. 1 shows a scraper-chain conveyor 1 installed along a working face not illustrated, said conveyor being composed of individual channel sections 1 a, 1 b, 1 C and so on interconnected pivotably vertically and horizontally to a limited extent. The scraper chain belt endlessly circulating in the conveyor 1 has been omitted for the sake of simplicity of illustration.

At the backfilling side of the conveyor 1, there is provided a guide rail 2. The guide rail 2 is also composed of individual sections 2a, 2b, 2c and so on. The length of each of these sections generally corresponds to the length of each conveyor channel section 1 a, 1 b, 1 C and so on. Each guide rail section 2a, 2b, 2c and so on consists of a metal plate 3 secured to the side wall of the conveyor 1 facing backfilling and a pipe 4 welded along the upper edge of the metal plate 3 (see also Fig. 2).

At the scraper chain conveyor 1, a cross cut winning machine 5 in the form of a cutting machine is positively guided of which merely the machine body 6 has been illustreated. The cross cut winning machine 5 has a pivot arm 7 with a cutting roll 8 arranged at the end thereof. The machine body 6 is supported via three support feet 9, 10 and 11 on the one hand on a flange 12 formed by the upper part of the conveyor 1 at its side adjacent to the working face and on the other hand on the guide rail 2. The support feet 9 and 10 are located at the ends of the machine body 6 at the working-face side thereof, while the support foot 11 is generally provided in the middle of the length of the machine at the backfilling side of the same. In this way, a welldefined three-point support is achieved.

A parallel guiding of the cutting machine 5 relative to the conveyor 1 is effected by guide feet 13 provided endwise of the machine body 6 at the backfilling side. These guide feet 13 are formed in such a way that, although they prevent a rotation of the machine body 6 relative to the conveyor 1, they nevertheless are not able to take over any support function. They are therefore telescopically and pivotally connected to the machine body 6. They have guide jaws 14 which encompass the pipe 4 of the guide rail 2.

Furthermore, it will be noted from Fig. 1 that the machine body 6 has two clamp feet 1 5 and 16 which in a manner to be described in closer detail hereinafter coact with the guide rail 2 and are connected with the machine body 6 via respectively two hydraulically pressurizable, thrust-piston-like advancing units 17, 1 8 and 19, 20 respectively. The piston rods 21 to 24 of the advancing units 1 7 to 20 are connected to the clamp feet 15 and 16, and the cylinders 25 to 28 are connected to the machine body 6.

In each clamp foot 15, 1 6 formed housing-like, there are provided a plurality of, for instance three, clamping element housings 29 arranged in an array in longitudinal direction (see Fig. 2). The clamping element housings 29 are arranged in longitudinal direction of the clamping feet 15 and 1 6 only with slide clearance both relative to one another and relative to the housing of the clamp feet 1 5 and 16, but with a substantially greater clearance in relationship thereto upwardly and downwardly and also laterally. The clamping element housings 29 thereby have the possibility of individually conforming themselves to the course of the guide rail 2.

In each downwardly open clamping element housing 29, a generally L-shaped clamping wedge 30 is vertically guided. The guiding is effected by the internal wall 31 of the housing 29 and a countersurface 32 as a component of an Lshaped angle 33 fixed to the housing 29. The horizontal limb 34 of the clamping wedge 30 is spaced relative to the housing cover 36 by a helical compression spring 35. Between the limb 34 and the horizontal limb 37 of the angle 33 there is arranged a thrust-piston-like releasing unit 38 which is composed of a piston 39 firmly connected to the angle 33 and a cylinder 40 vertically shiftable relative thereto. The pressure fluid connection of this releasing unit 38 is designated 41. It passes through the piston 39 to the work space 42.

The vertical limb 43 inclined unilaterally endwise, of the clamping wedge 30, coacts with a pivotable part 44 of a clamping jaw 45 located in the clamping element housing 29. The pivotable part 44 is connected via a longitudinally directed shaft 46 to a fixed part 47 of the clamping jaw 45. The clamping jaw 45 encompasses the pipe 4 of the guide rail 2 through a circumferential portion exceeding 1 80o.

The hydraulic lines to the previously described thrust-piston units 1 7 to 20, 38, the pressure sources and the required control means have not been illustrated for sustaining understandability of the drawings.

The operation of the advancing apparatus of the winning machine 5 is explained hereinafter in referring to Fig. 3.

The advancing apparatus has two hydraulic circuits controllable independent of one another regarding pressure, of which the work circuit has been illustrated in full lines and the auxiliary control circuit has been illustrated in interrupted lines. The winning machine 5 has been illustrated purely diagrammatically, and the same also applies for the clamp feet 1 5 and 16 and the advancing units 1 7 to 20 arranged at both sides of the clamp feet 15 and 16.

For pressure generation in the two hydraulic circuits, on the one hand a twin-control pump 48 and on the other hand an auxiliary circuit pump 49 are provided, which are driven by an electric motor 50. The adjusting elements 51 of the twincontrol pump 48 are pivoted to the piston rod 52 of a thrust-piston unit 54 at the one side pressurizable by a control fluid in counteraction to the resetting force of a helical compression spring 53. The pressure space 55 of this thrust-piston unit 54 receives control signals via a line 56 depending on the engaging momentum at the cutting roll 8. The pressure space 55 furthermore is in communication with the supply container 58 via a controllable restriction 57.The two supply lines 59 and 60 of the twin-control pump 48 respectively lead via a hydraulically shiftable reversing valve 6 > 1 and 62 to the advancing units 17, 18or19,20oftheclampfeet 15or 16. Itwill be noted that depending on the position of the reversing valves 61 and 62 at all times one piston space 63 or 64 and one piston rod space 65 or 66 of the advancing units 1 7 and 18 as well as one piston space 67 or 68 and one piston rod space 69 or 70 of the advancing units 19 and 20 jointly, i.e. at the same time, are connected to the supply line 59 or 60.

In the auxiliary control circuit leading to the releasing units 38' and 38", there are incorporated two limit switches 71 and 72 which are secured to the machine body 6 in a manner not illustrated in closer detail and are shiftable at the end of each work or neutral stroke of the advancing units 1 7, 18 or 19, 20 by the clamp feet 1 5 or 1 6 in counteraction to the resetting force of springs 73, 74. In the illustrated inoperative position, the limit switches 71 and 72 are in a locking position.

From the limit switches 71 and 72, line sections 75 and 76 lead via an automatically unlockable dual check valve 77 to the control connections 78 and 79 of a precontrol valve 80.

Said precontrol valve 80 is positioned in a line section of the auxiliary control circuit between the auxiliary circuit pump 49 and control connections 81 and 82 or 83 and 84 of the reversing valves 61 or 62. Depending on which of the limit switches 71 or 72 is operated by the clamp feet 1 5 or 16, the precontrol valve 80 shifts into the one or the other position, thereby the control fluid pumped by the auxiliary circuit pump 49 either being passed to the control connections 82 and 83 or the control connections 81 and 84 of the reversing valves 61 and 62.

Also, it will be noted that between the precontrol valve 80 and the control connections 81 and 82 or 83 and 84 of the reversing valves 61 or 62 there is incorporated a manually operable control valve 85. By means of this control valve 85 consequently the direction of movement of the winning machine 5 is able to be determined.

Fig. 3 in addition thereto permits to recognize that in the auxiliary control circuit between the auxiliary circuit pump 49 and the releasing units 38' and 38" there are incorporated check valves 86 and 87 locking to the releasing units 38' and 38". These check valves 86 and 87 are in communication via opening control lines 88 and 89 with the auxiliary control circuit between the precontrol valve 80 and the control connections 81 and 82 or 83 and 84 of the reversing valves 61 or 62.Furthermore, it will be appreciated that to the line sections 90 and 91 between the releasing units 38' or 38" and the check valves 86 or 87 there are connected further check valves 92 or 93 locking to the supply container 58, which check valves in turn are hydraulically unlockable via control lines 94 or 95, which are connected to the control lines 89 or 88 which lead to the check valves 87 or 86 connected to the respective other control line section 91 or 90.

In Fig. 3 a position of the winning machine 5 has been assumed in which an advancing operation is to be effected in the drawing plane to the right.

The work fluid applied to the supply sections 59 and 60 passes via the reversing valves 61 and 62 to the piston spaces 63 or 68 of the advancing units 1 7 or 20 and into the piston-rod spaces 66 or 69 of the advancing units 18 or 19. The clamp foot 1 6 is arrested at the guide rail 2, and the clamp foot 1 5 is released. As a result thereof, the winning machine 5 is shifted relative to the clamp foot 1 6 to the right in the drawing plane.When the stroke end of the advancing units 1 7 to 20 has been reached, for instance the clamp foot 1 5 contacts the limit switch 72 and shifts it into a position in which the control fluid passes from the auxiliary circuit pump 49 via the limit switch 72 and the automatically unlockable dual check valve 77 to the control connection 79 of the precontrol valve 80. This reverses so that the control fluid now is applied via the control line 89 simultaneously to the check valves 92 and 87.

The valves 92 and 87 open, so that initially the pressure in the releasing unit 38' is able to be relieved via the section 90 to the supply container 58 and a compression spring 35' arrests the clamp foot 15 at the guide rail 2. At the same time, the control fluid passes via the check valve 87, the line section 91 to the releasing unit 38" and terminates the clamping action of the clamp foot 16.

At the same time, the control fluid with the precontrol valve 80 reversed passes to the control connections 81 and 84 of the reversing valves 61 and 62 and shifts them into the other direction so that now via the supply sections 59 and 60 the piston spaces 64 and 67 of the advancing units 18 and 19 and the piston rod spaces 65 and 70 of the advancing units 17 and 20 are simultaneously pressurized. The winning machine 5 performs a further advancement movement to the right in the drawing plane, namely in clamping the clamp foot 1 5 with the clamp foot 16 released.

When now the advancing units 1 7 to 20 again reach the stroke end, the limit switch 71 is contacted, and a reversion of the precontrol valve 80 is again effected into the illustrated position. In this position, the control fluid initially passes into the control line 88 downstream of the precontrol valve 80, the check valve 93 thereby being opened and thus the releasing unit 38" being relieved. At the same time, the check valve 86 is opened so that the control fluid passes to the releasing unit 38' via the control line 90 and same is again pressurized in counteraction to the resetting force of the helical compression spring 35'. Now, the clamp foot 16 is again arrested at the guide rail 2, and the clamp foot 1 5 is relieved, so that a further advancement to the right in the drawing plane is able to be effected.

Claims (12)

Claims

1. An advancing apparatus for a winning machine positively guided along a cross cut conveyor, in particular of a cutting type, preferably for the side area of a cross cut, having two clamp feet arranged offset relative to one another in direction of movement of the winning machine, said clamp feet being connected by longitudinally directed, hydraulically pressurizable thrust-pistonlike advancing units to the winning machine, alternatingly arrestable at a guide rail provided at the cross cut conveyor and provided with hydraulically pressurizable thrust-piston-like releasing units, and furthermore possessing a hydraulic control automatically alternatingly pressurizing with work fluid or relieving from the work pressure the thrust-piston units, wherein each clamp foot is connected via two oppositely directed advancing units shiftable simultaneously in counterdirection to the winning machine and is arrestable by mechanical clamp elements forming a component of the clamp at the guide rail, the clamping of the clamping elements being releasable by pressurizing a releasing unit, the releasing units of the clamp feet being hydrulically interlocked mutually.

2. An advancing apparatus as claimed in claim 1, wherein the advancing units are pressurizable by a twin-control pump adjustable depending on the engagement momentum existing at the tools of the winning machine via two separate supply lines.

3. An advancing apparatus as claimed in claim 2, wherein into the supply lines between the twincontrol pump and the advancing units there are incorporated reversing valves which are hydraulically controllable depending on the position of limit switches associated with the winning machine and coacting with the clamp feet.

4. An advancing apparatus as claimed in claim 3, wherein both the limit switches and the control connections of the reversing valves are positioned in an auxiliary control circuit which is pressurizable by an auxiliary circuit pump which is connected to a motor possibly also driving the twin-control pump.

5. An advancing apparatus as claimed in claim 4, wherein into the auxiliary control circuit between the auxiliary circuit pump and the control connections of the reversing valves there is incorporated a precontrol valve hydraulically reversible depending on the position of the limit switches.

6. An advancing apparatus as claimed in claim 5, wherein into the control lines between the limit switches and the control connections of the precontrol valve there is incorporated an automatically unlockable dual check valve.

7. An advancing apparatus as claimed in any one of the preceding claims, wherein the releasing units only pressurizable unilaterally are connected ta the auxiliary control circuit via hydraulically unlockable check valves.

8. An advancing apparatus as claimed in claim 7, wherein the check valves locking toward the releasing units are repectively connected via an opening control line to the auxiliary control circuit between the precontrol valve and the control connections of the reversing valves, to the line sections between the check valves and the releasing units further check valves being connected locking toward the supply container, said further check valves respectively being connected via an opening control line to the control line which leads to the check valve connected to the other line section.

9. An advancing apparatus as claimed in claim 4 or any one of claims 5 to 8, wherein into the auxilary control circuit between the precontrol valve and the control connections of the reversing valves there is incorporated a control valve preferably reversible manually.

10. An advancing apparatus as claimed in claim 1, wherein the clamping elements have a guided clamping wedge which is pressurizable in direction of a clamping jaw encompassing the guide rails by means of a spring and in counterdirection by means of a releasing unit.

11. An advancing apparatus as claimed in claim 1 or 10, wherein the clamping elements are respectively arranged in housings which are inserted in the clamp feet likewise formed housing-like without any substantial clearance in longitudinal direction thereof, but with clearance in transverse and vertical direction.

12. An advancing apparatus for a winning machine, substantially as herein described with reference to and as illustrated by the accompanying drawings.

1 3. Any novel feature or combination of features as disclosed herein.